The Importance of Cribs

[Anonymous]

Hello!

Still very new to the whole ciphering business, however today I had a question about some quite advanced ciphering and wanted to know if any of you super intelligent people could solve it since I can’t!

Anyway, I get that cribs are an important part of code breaking. I’m waiting for the day where I’m not using a crib in challenge a (I won’t put which one I look for here, but it should be pretty obvious). However, when you get to advanced techniques, are there any ways to get around using them?

Say for instance I applied a standard columnar transposition cipher to an ADFGVX cipher, which would then split up pairs of letters. Would there be ways of working around that without a crib? Seems pretty crazy to me!

Thanks so much for the help!

[Anonymous]

If you replace each pair of letters with a single capital letter (doesn’t matter which letters yet) and then use letter freqeuncy to attempt to work out what all the letters are simply by their orders in how common they are (computers are helpful for this, I use a friends program). This will of course be inaccurate but you then just go through it using find and replace to change all the incorrect letters to lowercase correct versions (to stop you recorrecting them later make sure your find and replace is case sensitive) by seeing what seems to fit. This won’t use cribs but is pretty inefficient so I would still advise using cribs. Please ask if there is anything you are unsure about and also, I don’t claim to be super intelligent but I have been ciphering for a while both on and off Cipher Challenge.

[Anonymous]

As a code breaker who has solved many vigenere ciphers. In this way, I can say that the method I invented for cracking vigenere ciphers without a crib is extremely useful. One can work out the key length of an encrypted text by checking the index of coincidence of individual columns, and working out the average IoC for every key length. (Snip)

[Author]

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